Self-adjusting brake



Jan. 7, 1936. F. c. RUNYAN SELF ADJUSTING BRAKE 7 Filed March 21, 1935 //Vl/EN 701B [6. EU/Y VAN A rroe/vz Patented Jan. 7, 1936 PATENT OFFICE" SELF-ADJUSTING BRAKE ,Frank C. Bunyan, Overland, Mo.

Application March 21, 1935, Serial No. 12,140

10 Claims.

This invention relates generally to brakes, and more specifically to a brake of the type which includes a brake drum or equivalent element into and out of. contact with which brake shoes or other braking members are moved, the predominant object or the invention being to provide an improved brake of this general type which has associated therewith means for automatically adjusting the -o "positions of the shoes or other 0. braking members so as to maintain predetermined precise clearance between the shoes or other braking members and the brake drum or equivalent element, regardless of wear of the parts or expansion and contraction of the brake 15 drum or equivalent element caused by heating and cooling thereof.

Prior to this invention considerable effort was made to produce a brake structure, the shoes of which were automatically adjustable in a man- '20 ner to maintain predetermined clearance between the-shoes and the brake drum, and while these efforts were successful in many cases in so far as the limited result of automatic movement of the shoes toward the brake drum was concerned, the

25 producers of these automatically adjusted brake structures" overlooked one extremely important factorwhich prevented such's'tructures from operating with therequired efliciency; The factor referred to is the fact that brake drums become- 30 heatedasa result of repeated and long application of the brake, and because of such heating ofth brake druins and the subsequent cooling thereof the expand and contract.

The adjustment of the brakeshoes relative to 35 the brakedrumfin'thecase of each automatically adjusted brskstru mre withiwhich I am familiarfis nres ponseto "increasejof the movement or tl'i'e brakeshoes' relative to? the brake drum, and this-increase on movement may result from 40 weari*the"brakex"linings or expansionof the u brake drum. when; in the operation or these previouslwknown v structures ithe movement or theibria'ke' shoes. was .increasdyithe r oiifffs positions 1 OfEalthGyShQfiS'j mereiautomaticallyfiadiusted toward creased due to expansion of thedrum, the shoes cooled, and contracted relative to the shoes as 5 a result of such cooling, the clearance wasdecreased in proportion to the degree of contraction of the drum, with the result that the proper clearance between the shoes and the drum was not present, andfrequently clearance was entirely eliminated, with the result that the drum and shoes were positively locked together.

The brake structure disclosed herein is so constructed and arranged that when the movement of the shoes relativeto the drum is increased due to wear of the brake linings or expansion of a the drum, the oil positions of the shoes are automatically adjusted outwardly so as to reestablish the proper clearance. However, when the increase of. the shoe movement is due to expansion T of the drum and the drum subsequently contracts due to cooling thereof, the structure disclosed herein operates in a manner to readjust the shoes so as to re-establish the-proper clearance between the shoes and the contracted drum.

Fig. 1 is a fragmentary, sectional view illustrating a brake structure constructed and arranged in accordance with this invention. J

Fig. 2 is a sectional view taken approximately on'line 2-2 of Fig. 1. Fig. 3 is a sectional view taken approximately on line 3-3 of Fig. 1. & Fig. 4is a sectional view taken approximate lyonllne44ofFig .1. f" Fig. 5 illustrates a modified form of the invention.

Fig. 6 is an enlarged, fragmentary yielwjhpartly, j v

insection and, partly injelefvation, of aparti'of the "improved brake structure.

In the drawing,jwherei are, sliownior thel pur i 40 off positions by a coil spring H. The particular brake structure illustrated in the drawing is hydraulically operated, said structure including a wheel cylinder J provided with piston means K movable in response to pressure on a brake pedal (not shown), so as to operate the shoes and move the brake linings thereof into braking contact with the braking face of the brake drum.

Supported by the brake shoe 0 illustrated in Fig. 1 in contact with the web portion C thereof is an angularly shaped gripping element I, which at its upper end is provided with an extended portion 2 in which an elongated opening 3 is formed. Extended through the opening 3 referred to is a pin 4 which is provided with an enlarged head 5 that contacts loosely with the outer face of the gripping element I. The pin 4 at the end opposite to the headed end thereof is of reduced diameter, and this reduced portion of the pin is screwed, riveted, or otherwise fixedly located in an opening formed in the web portion of the shoe C, the shoulder between the full diameter portion of the pin and the reduced diameter portion thereof contacting with a face of said web portion of the shoe. The gripping element I is provided with an opening 6 which is open at opposite sides of the element, as shown most clearly in Fig. 6. This opening 6 is open also at the rear face of the element I, or, in other words, the face thereof which contacts with the web portion of the shoe, and is closed at the forward face of the gripping element by a portion of the element.

Supported by the shoe C is abar I which at one end is provided with a vertically elongated opening 8, this elongated opening having a pin 9 extended therethrough which is rigidly supported by and extends from the backing plate ,,D, as shown in Fig. 4. At its opposite end the bar 1 is loosely extended through a metallic strap I0, which is fixedly attached to the web portion of the shoeysaid strap being provided with an' outwardly formed portion II) which embraces the bar I. The bar I contacts with a'face of the web portion of the shoe C, andof said gripping element, and gripping faces 6 which are substantially parallel with respect to the top and bottom faces of the bar I (Fig. 6).

At a point beneath .the location of the metallic strap I0 the web portion of the shoe C is pro- -vided with a boss II which slidingly supports a' rod I2. At its inner end this rod is cut away, as indicated at I3 in Figs. 2 and 3, to provide a. portion I4 of reduced thickness which overlies the gripping element I adjacent to the lower end thereof, and at the point where this reduced portion of the rod joins the full diameter portion thereof a shoulder I5 is provided, which, when the brake shoe is in the off position, contacts with a side face of the gripping element I (Fig. 3). At its opposite end the rod I2 is provided with a head portion comprising an annular flange I6 and an extended portion I1, and this head portion supports a drum-contacting element I8. Preferably this drum-contacting element I8 is formed of a material which will wear a slight degree more rapidly than the brake lin- 1) to which a coil spring 20 is attached, the opposite end of said coil spring being connected to the lower end portion of the gripping element I. At the end of the gripping element l opposite to the end thereof at which the coil spring 20 is 5 attached a coil spring 2| is arranged, which is connected to said end portion of the gripping element and to a pin 22 extended from the backing plate D.

In considering the operation of the improved 10' braking structure disclosed herein, it is to be noted that when the shoe C is in its 01f position the pin 4 is in contact with the inner wall of the elongated opening 3, as shown in Fig.

1. Also, at such time the shoulder I5 of the rod 5 I2 is in contact with a side face of the gripping element I, while a space 23 is present between the outer end face of the boss II and the annular flange l6 of the rod l2. It is also important to note that the space between the forward por- 20 tion of the pin 4 and the forward wall of the elongatedopening 3 is the same as the predetermined clearance between the outer face of the brake lining and the inner face of the drum with which the brake lining contacts during ap- 5 plication of the brake, ten one-thousandths of an inch, for instance, while the space 23 between an end of the boss II and the annular flange I6 of the rod I2 is less than the space mentioned, or approximately seven one-thousandths of an inch. Likewise, it is to be noted that when the brake shoeis in the off position the drumcontactin'g element I8 extends beyond the outer face of the brake lining F of the shoe so that its outer drum-contacting face is spaced approximately three one-thousandths of an inch from the inner face of the drum.

The coil spring 2| tends to draw the upper end of the gripping element I inwardly, and as a result thereof the faces 6 of the opening 6 of the gripping element grip the top and bottom faces of the bar I tightly, so there can be no relative movement betweenthe upper end portion of the gripping element and said bar 1. Assume, now, that the shoe C is moved toward the braking face of the brake drum by pressure on a brake pedal associated with the braking structure. The bar I is held immovable by the pin 9 which is fixed to '-the backing plate,- and the gripping element is .longitudinally through the elongated opening3 of the gripping element. The space between the forward portion of the pin 4 and the forward wall of the elongated opening 3 is ten one-thousandths ofan inch, the same as the clearance between the brake lining and the braking face of the drum, hence it no wear is produced by application of the brake lining to the brake drum the braking action will be performed without changing the position of the gripping element I. Also, when the brake shoe is moved toward the brake drum as described, the seven one-thousandths of an inch space 23 will be initially taken up, after which the drum-contacting element will be moved an additional three one-thousandths of an inch into contact with the braking face of the drum. This three one-thousandths of an inch movement of the drum-contacting element causes the shoulder 70 I5 of the'rod I2 to be moved three one-thousandths of an inch away from the face of the gripping element with which'it normally on--- tacts, but this does not result in movement of the gripping element due to the fact that said grip ping element is in gripping engagement with the bar 1.

Assume, however, that wear has taken place when the brake lining is applied to the braking face of the brake drum. In this event the shoe will be compelled to move more than the predetermined ten one-thousandths of an inch to properly set the brake, and during this additional movement of the brake shoe the upper end of the gripping element I will be carried forwardly by the pin 4 in contact with the forward wall of the elongated opening 3. This forward movement of the gripping element relieves the grip between the gripping element and the bar I and permits the gripping faces 6 to slide longitudinally of the top and bottom faces of said bar. Now, when the pressure on the brake pedal is relieved the coil spring 2! will again draw the gripping faces 6 into gripping contact with the bar I but at the ad- Vance points thereof to which they have been moved by the additional movement necessary to set the brake, and the rearward movement of the shoe will be arrested by the pin 4 contacting with the inner wall of the elongated opening, which is the .oif position stop of the shoe, at a point closer to the drum than was previously the case. Thus, as the brake lining is subjected to wear by application of the brake, the inner wall of the elongated opening of the gripping element which constitutes the ofi position stop of the shoe is automatically adjusted toward the braking face of the brake drum to compensate for the wear, whereby a precise clearance between the outer surface of the brake lining and the braking face of the drum is maintained at all times.

Thus far in this description of the operation of the invention additional movement of the brake shoe C, because of wear of the brake lining alone, has been referred to as the cause of additional movement of the shoe toward the drum. Such additional shoe movement is caused also by expansion of the drum as the result of heating due to repeated or long application of the brake. When the brake drum B expands the shoes are adjusted outwardly toward the braking face of the drum in the manner already explained in connection with the wearing away of the brake linings, so as to maintain theproper clearance between the brake linings and the drum. The ex panded drum naturally contracts when it cools,

and when this contraction takes place the contracting drum contacts with the drum contacting element l8 and continued contraction of the drum moves the rod l2 inwardly. This inward movement of the rod 12 moves the lower end por-L tion of the gripping element l inwardly, thereby relieving the gripping action between the gripping element 1 and the bar I, and permitting the 'drum and said drum contractsdue to. cooling thereof, the shoe-adjusting mechanism is readjusted to again provide the proper clearance between the shoes and the contracted drum.

In; Fig. 5 I have shown a modified form of the invention in accordance with which the drumcontacting element I8 is supported by an extension i formed on the gripping element I. In this form of the invention the shoe C is provided with abutments II which contact with an abutment l6 formed on the drum-contacting element 18 so as to move said drum-contacting element toward the drum with the shoe. Also, the drum-contacting element is connected to the gripping element by a coil spring 20. The operation of the mechanism shown in Fig. 5 is substantially the same as that of the corresponding parts illustrated in Fig. 1. Y While I have shown only one brake shoe in Fig. 1, it is to be understood that each brake shoe of a braking structurefwill be provided with the shoe-adjusting mechanism illustrated in Fig. l.

I claim:

1. A brake comprising a brake drum, a brake shoe movable toward and from said brake drum,

a brake lining, said brake shoe being so arranged that predetermined clearance is present between said brake shoe and said brake drum when the brake shoe is in inactive position, automatically adjusted means including elements capable of relative movement for maintaining said predetermined clearance as the degree of movement of the brake shoe toward the braking position is increased because of wearing away of the brake lining or expansion of the brake drum, and means for automatically re-adjusting said automatically adjusted means when said brake drum contracts after expansion thereof, the last-mentioned means during readjustment of said automatically adjusted means'acting to change the relative. positions of said relatively movable elements of termined clearance as the degree of movement -of the brake shoe toward the braking position is increased because of wearing away of the brake lining or expansion of the brake drum, and means actuated by said brake drum for automatically re-adjusting said automatically adjusted means when said brake drum contracts after expansion thereof, the last-mentioned means during readjustment of said automatically adjusted means acting to change the relative positions of said relatively movable elements of said automatically adjusted means.

Cal

3. A brake comprising a brake drum, abrake' shoe movable toward and from said brake drum, a brake lining associated with said brakeshoe, said brake shoe being so arranged that predetermined clearance is present between said brake lining and said brake drum when the brake shoe is in inactive position, automatically adjusted means for maintaining said predetermined clearance as the degree of movement of the brake shoe toward the braking position is increased because of wearing away of the brake lining or expansion of the brake drum, and means including an element movable into and out of contact with said brake drum for automatically re-adjusting said automatically adjusted means in response to movement imparted thereto by contraction of the brake drum after expansion thereof.

4. A brake comprising a brake drum, a brake shoe movable toward and from said brake drum, a brake lining associated with said brake shoe, said brake shoe being so arranged that predetermined clearance is present between said brake lining and said brake drum when the brake shoe is in inactive position, automatically adjusted means for maintaining said predetermined clearance as the degree of movement of the brake shoe toward the braking position is increased because of wearing away of the brake lining or expansion of the brake drum, and means including an element movable with said shoe into and out of contact with said brake drum for automatically re-adjusting said automatically adjusted means in response to movement imparted thereto by contraction of the brake drum after expansion thereof.

5. A brake comprising a brake drum, a brake shoe movable toward and from said brake drum, a brake lining a-sociated with said brake shoe, said brake shoe being so arranged that predetermined clearance is present between said brake lining and said brake drum when the brake shoe is in inactive position, automatically adjusted means for maintaining said predetermined clearance as the degree of movement of the brake shoe toward the braking position is increased because of wearing away of the brake lining or expansion of the brake drum, and means including an element carried by said shoe and movable therewith into and out of contact with said brake drum for automatically re-adjusting said automatically adjusted means in response to movement imparted thereby by contraction of the brake drum after expansion thereof.

6. A brake comprising a brake drum, a brake shoe movable toward and from said brake drum, a brake lining, said brake shoe being so arranged that predetermined clearance is present between said brake shoe and said brake drum when the brake shoe is in inactive position, automatically adjusted means including elements capable of relative movement for maintaining said predetermined clearance as the degree of movement of the brake shoe toward the braking position is increased because of wearing away of the brake lining or expansion of the brake drum, and means for automatically re-adjusting said automatically,

adjusted means when said brake drum contracts "after expansion thereof, said readjusting means during readjustment of said automatically adjusted means acting to change the relative positions of said relatively movable elements of said automatically adjusted means, said auto-- matically adjusted means and the means for readjusting same being supportedby said shoe.

'7. A brake comprising a brake drum, a brake shoe movable toward and from said brake drum,

a brake lining associated with said brake shoe, said brake shoe being so arranged that pr-edetermined clearance is present between said brake lining and said brake drum when the brake shoe is in inactive position, automatically adjusted means for maintaining said predetermined clearance as the degree of movement of the brake shoe toward the braking positionis increased because of wearing away of the brake lining or expansion of the brake drum said means including a member relative to which the brake shoe moves, a gripping element supported by said brake shoe and adapted to grip said member, an abutment carried by said brake shoe and adapted to contact with an abutment face on said gripping element which provides the inactive position stop for the brake shoe, said gripping element being adjusted relative to said member in response to excessive movement of said brake shoe toward the braking position, and means for automatically re-adjusting said automatically adjusted means when said brake drum contracts after expansion thereof.

8. A brake comprising a brake drum, a brake shoe movable toward and from said brake drum, a brake lining associated with said brake shoe, said brake shoe being so arranged that predetermined clearance is present between said brake lining and said brake drum when the brake shoe is in inactive position, automatically adjusted means for maintaining said predetermined clearance as the degree of movement of the brake shoe toward 'the braking position is increased because of wearing away of the brake lining or expansion of the brake drum, said means including a member relative to which the brake shoe moves, a gripping element supported by said brake shoe and adapted to grip said member, and abutment carried by said brake shoe and adapted to contact with an abutment face on said gripping element which provides the inactive position stop for the brake shoe, said gripping element being adjusted relative to said member in response to excessive movement of said brake shoe toward the braking position, and means including an element movable into and out of contact with said brake drum for automatically re-adjusting said automatically adjusted means in response to movement imparted thereto by contraction of the brake drum after expansion thereof.

9. A brake comprising a brake drum, a brake shoe movable toward and from said brake drum, a brake lining associated with said brake shoe, said brake shoe being so arranged that predetermined clearance is present between said brake lining and said brake drum when the brake shoe is in inactive position, automatically adjusted means for maintaining said predetermined clearance as the degree of movement of the brake shoe toward the braking position is increased because of wearing away of the brake lining or expansion of the brake drum, said means including a member relative to which the brake shoe moves, a gripping element supported by said brake shoe and adapted to grip said member, an abutment carried by said brake shoe and adapted to contact with an abutment face on said gripping element which provides the inactive position stop for the brake shoe, said gripping element being adjusted relative to said member in response to excessive movement of said brake shoe toward the braking position and means including an element movable with said shoe into and out of contact with said brake drum for automatically re-adjusting said automatically adjusted means in response to movement imparted thereto by contraction of the brake drum after expansion thereof.

10. A brake comprising a brake drum, a brake shoe movable towardand from said brake drum, a brake lining associated with said brake shoe, said brake shoe being so arranged that predeter mined clearance is present between said brake lining and said brake drum when the brake shoe is in inactive position, automatically adjusted means for maintaining said predetermined clearance as the degree of movement of the brake shoe toward the braking position is increased because of wearing away of the brake lining or expansion of the brake drum, said means including a member relative to which the brake shoe moves, a gripping element supported by said brake shoe and adapted to grip said member, an abutment carried by said brake shoe and adapted to contact with an abutment face on said gripping element which provides the inactive position stop for the brake shoe, said gripping element being adjusted relative to said member in response to excessive movement of said brake shoe toward the braking position, and means including an element movable with said shoe into and out of contact with said brake drum and adapted to impart movement to said gripping element for automatically re-adjusting said automatically adjusted means in response to movement imparted thereto by contraction of the brake drum after expansion thereof.

FRANK C. RUNYAN. 

